class Solution {
public:
    int findKthLargest(vector<int>& nums, int k) {
        srand(time(NULL));
        return qsort(nums, 0, nums.size() - 1, k);
    }

    int qsort(vector<int>& nums, int l, int r, int k) {
        if (l == r) return nums[l];

        int key = getRand(nums, l, r);

        int left = l - 1, right = r + 1, i = l;
        while (i < right) {
            if (nums[i] < key) swap(nums[++left], nums[i++]);
            else if (nums[i] == key) i++;
            else swap(nums[i], nums[--right]);
        }
        int c = r - right + 1, b = right - left - 1;
        if (c >= k) return qsort(nums, right, r, k);
        else if (b + c >= k) return key;
        else return qsort(nums, l, left, k - b - c);
    }

    int getRand(vector<int>& nums, int left, int right) {
        return nums[rand() % (right - left + 1) + left];
    }
};
